塔里木盆地中-下寒武统沉积相带与储盖关系

Discussion on the relationship between sedimentary facies and reservoir-cap rocks of the Middle-Lower Cambrian in Tarim Basin,China

探讨塔里木盆地中-下寒武统沉积相带展布与储层、盖层发育规律。通过分析最新钻井的岩石结构、沉积序列,刻画优势储层相带、盖层发育规律,结果表明:肖尔布拉克组自塔南古隆起向北发育混积潮坪-碳酸盐缓坡沉积体系,盆地北部沙雅-轮探1井一带为中缓坡外带;吾松格尔组沉积期,巴楚一带因水体局限而发育膏盐坪,塔北隆起区局部发育台内砂屑滩;中寒武世膏盐湖沉积体系中,台内仍有浅滩发育,阿瓦塔格组膏盐湖向北延伸至轮探1井一带;优势储层分为高能滩相白云岩储层和台内云坪相白云岩储层两大类,高能滩相白云岩储层由颗粒滩相储层和高能丘滩相储层组成;沙依里克组发育2套稳定的膏盐岩盖层,阿瓦塔格组发育3套膏盐岩盖层,并逐渐增厚,分布范围向塔北扩大。5套膏盐岩盖层有效封盖了下伏的高能滩相、云坪相白云岩储层,白云岩-膏盐岩的岩石组合、高能滩相-膏盐湖的垂向沉积序列是塔里木盆地中-下寒武统油气成藏的重要前提。

Through the analysis of rock texture and sedimentary sequence of the latest drilling in the Middle-Lower Cambrian in Tarim Basin,the characteristics of dominant reservoir facies zones and cap rock development are described,and the distribution of sedimentary facies zones and the development law of reservoir and cap rock are discussed.The results show that the mixed tidal flat carbonate gentle slope sedimentary system is developed in the Xiaoerbulak Formation from the paleo-uplift in the south of Tarim Basin to the north,while the middle gentle slope outer zone is developed in the Shaya-Runtan 1 Well area in the north of the basin.During the sedimentary period of Wusonger Formation,gypsum and salt flats were developed in Bachu area due to the limitation of water body,and local sand shoal was developed in Tabei uplift area.In the Middle Cambrian salt-lake sedimentary system,there are shoals developed in the platform,and the salt-lake of Awatage Formation extends northward to Well Luntan 1.The dominant reservoirs in the study area are composed of high energy shoal facies dolomite reservoir and dolomite flat facies dolomite reservoir in the platform,and the high energy shoal facies dolomite reservoir is composed of grain stone facies reservoir and high energy bioherm facies reservoir.In terms of cap rocks,there are two stable caps of gypsum salt rocks in Shayilike Formation and three caps of gypsum salt rocks in Awatage Formation,which are gradually thickening and extending to the north of the Tarim Basin.It is considered that,such conditions as high energy shoal facies and dolomite flat facies reservoirs under the effective sealing of five sets of gypsum rocks,the rock assemblage of dolomite and gypsum rocks,and the vertical sedimentary sequence of high energy shoal facies and gypsum salt lake,are important prerequisites for hydrocarbon accumulation in the Middle-Lower Cambrian in Tarim Basin.